Nanoparticles and preparation method thereof

ABSTRACT

The present invention relates to a nanoparticle, a preparation method thereof, a stone removing device and its application. The nanoparticle includes a nanoparticle core made of a magnetic material, and a nanoparticle shell formed by attaching a surface modifier monomer to the nanoparticle core with an initiator and/or a crosslinking agent. The prepared nanoparticle can surround stones in ureter, and then small stone remaining in body can be removed quickly without damage from the body under the action of an externally applied magnetic field, that is, the stone can be drawn and moved without injuring ureteral wall, and meanwhile the nanoparticles are placed conveniently without shift.

TECHNICAL FIELD

The present invention relates to nanoparticles and methods of making the same. Further, the present invention also relates to a stone removing device containing nanoparticles and its application.

BACKGROUND ART

Urinary calculi/stone (urolithiasis) have an incidence as high as 5%-10%, and can be found in any part of kidney, bladder, ureter and urethra, in which stones in kidney and ureter are common. It is found in clinical observation that calcium-containing stones are the most common types of urinary stones, that is, about 70% to 80% of all urinary stones. At present, there are only a few cases of calcium-containing stones which pathological causes have been clearly revealed, while the causes for most of calcium-containing stones are not yet clear. According to chemical composition, stones can be divided into four categories: calcium-containing stones, infection induced stones, uric acid stones and cystine stones. Calcium-containing stones can be divided into following types: simple calcium oxalate, calcium oxalate with calcium phosphate, calcium oxalate with a small amount of uric acid; the main components of infection induced stones are ammonium magnesium phosphate and hydroxyapatite; uric acid stones can be divided into following types: uric acid, uric acid amine, or those containing a small amount of calcium oxalate in addition to the above ingredients; cystine stones can be divided into following types: simple cystine, or cystine with a small amount of calcium oxalate.

Soft/hard ureteroscopic lithotripsy is performed through natural channel of the human body, has the advantages of small trauma and definite lithothriptic effect, and is currently the main treatment means for most of ureteral stones and kidney stones. However, the current soft/hard ureteroscopic lithotripsy also has some deficiencies: 1) upper ureteral stones and fragments of stones in ureter may be easily brought back to kidney by the infused water or the recoil force of lithotripsy tools; 2) there is lack of a fast, safe and effective method to take out residual debris of stones in ureteral lumen and kidney calices. It is an an important mean to prevent ureteral stones from being recoiled back to kidney that a tool is used to block the ureter above the ureteral stones. At present, there are also some ureteral occluders in clinical practice, and such kind of stones blocking tools are also commonly used to remove stones. However, these ureteral occluders still have some shortcomings in actual use. Stone baskets (such as various stone baskets described in Patent Publication No. JP2009536081 A, DE19904569A1, WO2004056275A1, WO2011123274A1 are designed with a net bag) are the most commonly used stone interception and removal tools, which cross over stone and then are opened to form a net so as to prevent the upward drift of stone debris, and at the same time, the stone baskets are also used as stone removal tools to net and take out small stone debris. However, the amount of stone removed by the stone basket every time is limited, so that multiple feeds of ureteroscope are needed, while repeated injection of water and feeds of ureteroscope would increase the risk of residual debris drift; in addition, the stone basket can not completely seal the ureteral lumen, and there are still a chance that stones escape from the net; moreover, the edges of stones in stone basket may be easily squeezed out from basket holes, and thus may easily scratch the ureter wall when the stones are dragged and removed, thereby causing complications in severe cases.

In addition, CN105283140A describes a kit of a cross-linked gel for encapsulating urethral stones and/or debris of urethral stones. However, when a gel-containing magnetic reagent (mock) is added to an aqueous solution containing stones, the cationic polymer is dispersed substantially in the form of dissolving in a solvent rather than aggregates to the periphery of stones due to the principle of similar compatibility, which is not sufficient to magnetize stones and remove stones.

In summary, there is an urgent need for a material and method for removal of stones in urinary system that can collect stones, facilitate the stone taking, do not damage the ureteral wall when the stones are dragged, can be conveniently placed and are not easy to cause shift of stone.

Contents of the Invention

The present invention is aimed to solve the problem of residual stone debris and difficult removal thereof in the conventional soft/hard ureteroscopic lithotripsy. Therefore, a first object of the present invention is to provide a nanoparticle that can be used safely and efficiently to remove a stone located at a position such as kidney, ureter and so on in an urinary system, and the nanoparticle has excellent dispersibility. A second object of the present invention is to provide a method for preparing the nanoparticle with different morphological structures. A third object of the present invention is to provide a use of the nanoparticle in coordination with a selfmade magnetic probe rod system in an operation of urinary calculi; a fourth object of the present invention is to provide a use of the nanoparticle in manufacture of an article for removing a stone in urinary system.

According to the first aspect of the present invention, there is provided a nanoparticle comprising a nanoparticle core made of a magnetic material; and a nanoparticle shell formed by attaching a surface modifier monomer to the nanoparticle core with an initiator and/or a crosslinking agent.

According to some embodiments of the present invention, the nanoparticle comprises: a nanoparticle core made of a magnetic material; and a nanoparticle shell formed by in-situ modification of a surface modifier monomer to the surface of the nanoparticle core with an initiator and/or a crosslinking agent; wherein the surface of the nanoparticle after surface modification and functionalization has an amide bond or a carboxyl group, and the weight percentage of the shell is 0.5-45% (excluding end points), preferably 1-40%, more preferably 2-40%, further more preferably 1-15% or 2-15%, most preferably 1%, 2%, 15% or 40%, with regard to the weight of the nanoparticles.

According to some embodiments of the present invention, the nanoparticle comprises: a nanoparticle core made of a magnetic material; and a nanoparticle shell formed by in-situ modification of a surface modifier monomer to the surface of the nanoparticle core with an initiator and/or a crosslinking agent, wherein the surface of the nanoparticle after surface modification and functionalization has an amide bond or a carboxyl group, and the method for preparing the magnetic nanoparticle core is a co-precipitation method, wherein a solution of the magnetic material and a catalyst are added in the manner of electronic pump-assisted continuous dropping.

In another embodiment, the nanoparticle comprises: a nanoparticle core made of a magnetic material; and a nanoparticle shell formed by in-situ modification of a surface modifier monomer to the surface of the nanoparticle core with an initiator and/or a crosslinking agent; wherein the surface of the nanoparticle after surface modification and functionalization has an amide bond or a carboxyl group, and the method for preparing the magnetic nanoparticle core is a co-precipitation method, wherein the surface modifier monomer is added in the manner of electronic pump-assisted continuous dropping.

According to some embodiments of the present invention, the nanoparticle surrounds a stone through physical adsorption, chemical bonding, and photosensitive, thermosensitive, and pH-sensitive crosslinking; specifically, the mutual forces for binding and surrounding between the nanoparticles and the stone include: van der Waal's force that form an interacting surrounding, hydrophobic interaction, adsorption and surface deposition; covalent bonds formed between carboxyl-stone, including hydrogen bonds, ester bonds, amide bonds, and other covalent bonds; interacting physical entanglement and chemical crosslinking between chains.

According to some embodiments of the present invention, the nanoparticle core has a diameter of 2-50 nm, and a weight percentage of 30-95% with regard to the whole weight of the nanoparticle, and the magnetic material constituting the core includes a compound of Fe³⁺, Fe²⁺, Mn²⁺ or Ni²⁺, or a metal element selected from iron, nickel, copper, cobalt, platinum, gold, europium, gadolinium, dysprosium, terbium, or a composite or oxide of the aforementioned metals, or any one of the above items or a combination of two or more of the above items, preferably one of or a combination of any two of Fe³⁺, Fe²⁺, Mn²⁺ or Ni²⁺, more preferably Fe³⁺ and Fe²⁺ in a ratio of 15% to 85%, preferably 1:2.5 to 1.5:1. It should be noted that the method for preparing the nanoparticle used in the present invention can well control the size and dimension of the magnetic nanoparticle core; especially, in comparison with the nanoparticles prepared by other methods, among the parameters of the nanoparticle obtained in the present invention that relates to the biomedical application, the dispersibility of the nanoparticle is very good and less than 1.1.

According to certain embodiments of the present invention, the surface modifier includes a hydrophilic surface modifier with function response, a hydrophobic surface modifier with function response, a photosensitive surface modifier with function response, a thermosensitive surface modifier with function response or a pH sensitive surface modifier with function response, wherein the hydrophilic surface modifier includes acrylic acid, methacrylic acid, isobutyl acrylamide or poly N-substituted isopropylacrylamide; the hydrophobic surface modifier includes olefins, preferably polystyrene, polyethylene or oleic acid; the photosensitive surface modifier is selected from the group consisting of azos and quinolines and benzophenones (PVBP), preferably vinyl benzophenone; the thermosensitive surface modifier is selected from the group consisting of amphiphilic polymers with an amide bond, preferably polyacrylamide or poly N-substituted isopropylacrylamide; the pH-sensitive surface modifier is selected from the group consisting of polymers with a carboxyl group and a quaternary ammonium salt, preferably polyacrylic acid, dimethylaminoethyl ester and dimethylaminopropyl methacrylate.

According to certain embodiments of the present invention, the crosslinking agent includes 3-(methacryloyloxy)propyltriethoxysilane, divinylbenzene, diisocyanate or N,N-methylenebisacrylamide, and the initiator includes 3-chloropropionic acid, CuCl, 4,4′-dinonyl-2,2-bipyridine or potassium persulfate.

The second aspect of the invention provides a method of preparing the nanoparticle, including the steps of: a) preparing the nanoparticle core using the magnetic material; and b) forming the nanoparticle shell by in-situ linking the surface modifier monomer to the nanoparticle core by the initiator and/or crosslinking agent. As used herein, “in-situ” means that the surface modifier is directly attached to the surface of the nanoparticle core. The resulting modified nanoparticle has a size between 50 nm and 5000 nm, which varies according to different conditions.

According to some embodiments of the present invention, the nanoparticle core is composed of Fe₃O₄, MnFe₂O₄, γ-Fe₂O₃, or other nanoscale-sized ferrite particles, and these ferrite particles are prepared by the following steps:

dissolving a proportion of the metal salt-containing material in water;

feeding nitrogen to expel oxygen in the solution;

adding a catalyst at a room temperature of 20-30° C. to adjust the pH to 8-12, preferably 10;

keeping agitation and reaction for 20-40 minutes; and

reacting under condition of 50-100° C., preferably 70° C. water bath, for 20-40 minutes, then separating with a magnet and drying to obtain the magnetic nanoparticle core.

In a particular embodiment of the present invention, the oxygen-containing metal salt is FeCl₃.6H₂O and FeCl?₂.4H₂O, which are dissolved in water in a molar ratio of 15% to 85%, preferably 1:2.5 to 1.5:1, wherein the catalyst is aqueous ammonia. Fe₃O₄ nanoparticles can be obtained by following the above steps.

According to some embodiments of the present invention, the step b) includes dispersing the prepared nanoparticles in an aqueous solution, adding with an xylene solution of 3-chloropropionic acid, polystyrene, CuCl and 4,4′-dinonyl-2,2-bipyridine, wherein the molar ratio between the solution of iron particles and the reaction solution is 1:1; reacting the mixture for 15-30 hours, preferably 24 hours, at 130° C. under continuous agitation; and collecting the nanoparticles with a magnet, washing repeatedly with toluene to obtain hydrophobic polystyrene-surrounded magnetic iron oxide nanoparticles.

According to some embodiments of the present invention, the step b) includes dissolving and dispersing the resulting nanoparticle core into xylene, adding with a silane coupling agent, wherein the silane coupling agent, wherein the nanoparticles, xylene and silane coupling agent are added in a ratio of 95:5; reacting under the protection of nitrogen atmosphere at 20-100° C., preferably at 80° C., for 2-5 hours, preferably for 3 hours; washing with an alcoholic solvent (preferably absolute ethanol) and drying for 12 hours, dispersing in an aqueous solution under ultrasonic condition, adding with potassium persulfate; reacting under nitrogen protection, at 40-80° C. for 10 minutes, adding with acrylic acid to continue reaction at 40-80° C. for 1 hour, wherein the reaction temperature is preferably 70° C.; and separating with a magnet, washing and drying to obtain the polyacrylic acid-modified hydrophilic nanoparticles.

According to some embodiments of the present invention, the above step b includes: dissolving and dispersing Fe₃O₄ nanoparticles into xylene, and adding with a silane coupling agent, wherein the silane coupling agent (the ratio of the Fe₃O₄ nanoparticles and the silane coupling agent as added is 95:5); reacting under protection of nitrogen atmosphere at 80° C. for 2-5 hours, preferably for 3 hours; washing with an alcoholic solvent (preferably absolute ethanol) and drying for 12 hours, dispersing in an aqueous solution under ultrasonic condition, adding with potassium persulfate; reacting under nitrogen protection at 40-80° C. for 10 minutes, adding with a photosensitive monomer such as vinyl benzophenone, a thermosensitive monomer such as N-isopropylacrylamide, or a pH-sensitive monomer such as dimethylaminopropyl methacrylate, etc. (or a blended monomer of acrylic acid and styrene), reacting continuously for 1 hour at 40-80° C., preferably at 70° C.; and separating with a magnet, washing and drying to obtain the photosensitive, thermosensitiveor pH sensitive functional monomer-modified magnetic nanoparticles, respectively.

In certain embodiments of the present invention, the photosensitive monomer modification based on the hydrophilic surface modification includes: dissolving and dispersing the polyacrylic acid-modified magnetic nanoparticles in an alcoholic solvent, dispersing for 5-30 minutes under ultrasonic condition, then adding an initiator and a photosensitive monomer polyvinylbenzophenone, refluxing and reacting at agitation and 130° C. for 24 hours under condition that oxygen is kept out to prepare the photosensitive monomer-modified magnetic nanoparticles.

In the above embodiment, when aqueous ammonia is used as catalyst to prepare the nanoparticles, the method for dropping aqueous ammoniais performed in a continuous and dropwise manner with assistance of an electronic pump at a speed of 20-100 drops/minute, preferably 40-60 drops/minute; and when the magnetic material is an element material, the liquid monomer is added in a dropwise and continuous manner with assistance of an electronic pump, and the reaction is carried out under agitation with a speed of 100-1000 revolutions/minute, preferably 500-700 revolutions/minute.

It should be noted here that the particle size, distribution and morphology (such as shape of sphere, rod, diamond, etc.) of the obtained magnetic nanoparticle core can be relatively easily controlled under the synthetic methods and preparation conditions as we designed above. Furthermore, the surface-modified magnetic nanoparticles prepared by the above method have particle size and distribution superior to those of magnetic nanoparticles obtained by conventional preparation methods. As shown in the following table, the dispersibility index (PD.I.) of the obtained nanoparticles is basically close to 1.0, which clearly shows that the particle size distribution of the obtained particles is narrow. This is very important because, for in vivo biomedical applications, the size and dispersion of nanoparticles determine the breadth of their medical applications. The PD.I described herein for describing the dispersibility of nanoparticles is defined as follows:

PD.I.==<Rh ² >/<Rh> ²

wherein, Rh represents hydrodynamic radius of particle.

The nanoparticle core and the surface-modified magnetic nanoparticle have distribution PD.I. as shown in the following table:

Magnetic nanoparticle core After surface modification Diameter/nm 40-50 80-100 PD.I./a.u. 0.005 0.0055

In addition, as shown in FIG. 2, the structure of the nanoparticles obtained in the present invention is clear.

According to the third aspect of the present invention, there is provided a device for removal of stone, which can be used in the urinary system and consists of a magnetic nanoparticle in combination with a stone-removal magnetic probe rod system. The device for removal of stone comprises the above-mentioned nanoparticles of the present invention and an auxiliary stone-removal magnetic probe rod system. The device for removal of stone can be used for removing a stone in urinary system such as kidney stone, ureteral stone and bladder stone, etc., as well as removing a stone in human biliary system and a stone-like particle in other organs.

Specifically, the stone-removal magnetic probe rod system comprises a handle, a flexible rod, a magnetic field source, a magnetically permeable material section, etc., in which the handle may be provided with an AC or DC power supply, a power switch, a DC battery compartment and an AC plug; the flexible rod is made of a polymer material including, for example, PU, TPU, PE, PVC, NYLON, PEBAX and silicone rubber and the modified materials of the above materials, the magnetic field source made of a permanent magnet or electromagnet can be embedded in the flexible rod, and optionally a high performance magnetically permeable material is connected to the magnetic field source to form the flexible probe rod with different configurations, for example, the permanent magnet is placed in the middle or back end of the flexible rod, and the magnetically permeable material is placed in the distal end of the flexible rod, so that such configuration is more conducive to the treatment of renal stones under ureteroscope to avoid the situation that the distal end of the flexible rod becomes rigid due to the rigid structure of the permanent magnet or the electromagnet, so that such magnetic probe rod can be successfully inserted into the working channel of ureteroscope, and inserted into upper, middle and lower kidney calices to carry out stone removal operation when driven by the ureteroscope.

In the forth aspect of the invention, there is provided an article comprising the nanoparticle of the present invention, in which the nanoparticle is prepared in the form of a solution or powder.

The invention provides a novel preparation process for synthesizing hydrophilic, hydrophobic, thermosensitive and pH-sensitive as well as photosensitive magnetic nanoparticles, which has the advantages of simple preparation process, good repeatability and convenient application. By the hydrophobic interaction between the prepared hydrophobic nanoparticles and stones, the chemical bond interaction between hydrophilic nanoparticles and stones, and the polymerization of the photosensitive nanoparticles under illumination, the stones are surrounded; and the thermosensitive and pH-sensitive nanoparticles can surround stones through physically surrounding action in ureter; thereby, small stone remaining in body can be removed quickly without damage from the body under the action of an externally applied magnetic field, that is, the stone can be drawn and moved without injuring ureteral wall, and the nanoparticles are placed conveniently without shift.

The present invention is further described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the transmission electron microscope (TEM) images and the particle size distribution diagrams under dynamic light scattering for the cores with different morphologies obtained in Example 1 of the present invention.

FIG. 2 shows the particle size distribution diagram under dynamic light scattering for the monomer-modified nanoparticles obtained in Example 4 of the present invention; and TEM images of the monomer-modified nanoparticles obtained in Example 3 of the present invention.

FIG. 3 shows the hysteresis curves of the monomer-modified nanoparticle cores with different Fe³⁺/Fe²⁺ ratios in the synthesis of the nanoparticles obtained in Example 3 of the present invention.

FIG. 4 shows the graphs of stone separation for the photosensitive monomer-modified nanoparticle cores obtained in Example 4 of the present invention, and the graphs of separation performance for the nanoparticle cores synthesized with different Fe³⁺/Fe²⁺ ratios and modified with functional monomer.

FIG. 5 shows a graph of biocompatibility to 293t cells for the functional magnetic nanoparticles obtained in Example 4 of the present invention.

FIG. 6 shows a graph of stone separation with in vitro assistance for the nanoparticles obtained in Example 6 of the present invention.

FIG. 7 shows a graph of safety evaluation in body of animals for the nanoparticles of the present invention.

FIG. 8 shows an overall schematic diagram of the magnetic probe rod system for assisting stone removal in the present invention.

FIG. 9 shows a schematic view of the handle portion of the magnetic probe rod system for assisting stone removal in the present invention.

FIG. 10 shows a schematic view of the magnetic probe rod system with an AC power supply for assisting stone removal according to the present invention.

FIG. 11 shows a schematic view of the internal structure of the magnetic probe rod system using an electromagnet as magnetic field source according to the present invention.

FIG. 12 shows a schematic view of the magnetic probe rod system of the present invention which uses an electromagnet as magnetic field source and a magnetically permeable material section at distal end.

FIG. 13 shows a schematic view of the magnetic probe rod system of the present invention which uses a permanent magnet as magnetic field source and a magnetically permeable material section at distal end.

FIG. 14 shows a schematic view of the magnetic probe rod system of the present invention which uses a permanent magnet as magnetic field source and has not a magnetically permeable material section at distal end.

FIG. 15S shows a diagram of the principle of interaction between magnetic particles and stones.

FIG. 16 shows a diagram of agitation of the reaction system in steps 2-4) of the method for preparing the nanoparticles of the present invention, which uses a magnetic stirrer at a speed of 100-1000 revolutions/minute, preferably 500-700 revolutions/minute.

FIG. 17 shows a diagram of the steps 1-4) of the method for preparing the nanoparticles according to the present invention, in which aqueous ammonia and liquid monomer are added dropwise continuously and uniformly by an electronic pump at a rate of 20-100 drops/minute, preferably 40-60 drops/minute.

FIG. 18 shows the effect of addition mode of the surface modifier monomer on the particle dispersibility.

FIG. 19 and FIG. 20 show TEM images of the particles after continuous addition and dropping.

FIG. 21 shows the effect of the weight percentage of the nanoparticle shell with regard to the nanoparticle on the dispersibility of the nanoparticle.

SPECIFIC MODELS FOR CARRYING OUT THE INVENTION

The present invention is further illustrated below with reference to the accompanying drawings and specific examples. It should be understood that the following examples are only used to illustrate the present invention, rather than to limit the scope of the present invention.

According to a first aspect of the present invention, there is provided a magnetic nanoparticle with good dispersibility, capable of safely and efficiently removing stones in urinary system. The present invention provides a functional magnetic nanoparticle, comprising: hydrophilic, hydrophobic, photosensitive, thermosensitive, pH-sensitive magnetic nanoparticles, which morphology can be spherical, rod-shaped and the like, which structure can be of core-shell structure consisting of a magnetic core and a monomer modifier such as hydrophilic, hydrophobic, temperature sensitive, pH-sensitive or photosensitive surface modifiers as well as a small amount of initiator; in which the hydrophilic surface modifier forms a hydrophilic shell by polymerization to surround the magnetic nanoparticle core, including the hydrophilic materials with positive charges, negative charges and electricity neutrality; the hydrophobic surface modification is carried out by a poor water-soluble polymer or inorganic material; the other functional materials such as photosensitive, thermosensitive and pH-sensitive monomer modifiers may be polymerized by a crosslinking agent and embedded in a hydrophobic shell, or these monomer modifiers may be in-situ and directly attached to the surface of the core by an initiator and/or crosslinking agent.

Among the various kinds of responsive magnetic nanoparticles such as hydrophilic, hydrophobic, thermosensitive, pH-sensitive and photosensitive magnetic nanoparticles, the materials for synthesizing magnetic nanoparticle cores comprise Fe³⁺, Fe²⁺ and Mn²⁺, Ni²⁺ compounds, as well as metal elements such as iron (Fe), nickel (Ni), copper (Cu), cobalt (Co), platinum (Pt), gold (Au), europium (Eu), gadolinium (Gd), dysprosium (Dy), terbium (Tb), or composites and oxides of the metals, such as Fe₃O₄ or MnFe₂O₄, preferably iron, manganese or their compounds; also preferably, any one of them or any combination of two or more of them may be used; and the core has a size of 2-50 nm.

The preparation method of the magnetic nanoparticle core includes co-precipitation methods, emulsion methods, redox reaction or high-temperature high-pressure methods. The weight percentage of the magnetic nanoparticle core is 30% to 95% with regard to the total weight of the functional magnetic nanoparticle, taking the synthesis of Fe₃O₄ as example, the ratio of Fe³⁺ to Fe²⁺ is 15% to 85%, preferably 1:2.5 to 1.5:1 for Fe³⁺ and Fe²⁺.

The surface of the magnetic nanoparticle can be subjected to functional modification, such as hydrophilic modification, hydrophobic modification, and modification with photosensitive, thermosensitive and pH-sensitive materials.

According to a first embodiment of the present invention, there is provided a hydrophilically modified functional particle, wherein the core size is 2-50 nm, the magnetic nano-core has a weight of 30-95% with regard to the total nanoparticle; the hydrophilic surface modifier is a polycationic or an anionic polymer, such as acrylic acid, methacrylic acid and isobutyl acrylamide, etc., which weight percentage is 2-8% with regard to the whole hydrophobic magnetic nanoparticle. The magnetic core particle is attached on its surface with an initiator such as 3-chloropropionic acid or the like, then a polymer based on acrylic acid, methacrylic acid and isobutyl acrylamide or the like is modified on the particle surface with a crosslinking agent by a chemical reaction, such as radical, ring-opening polymerization and atom transfer radical polymerization (ATRP); the shape of the particle may be spherical, rod-shaped and layered, preferably spherical particles. The crosslinking to agent is 3-(methacryloyloxy) propyltriethoxysilane (MPS), divinylbenzene and diisocyanate or N,N-methylenebisacrylamide (MBA) and the like.

According to a second embodiment of the present invention, there is provided a hydrophobically modified functional particle, wherein the core has a size of 2-50 nm, the magnetic nano-core is 30-95% by weight with regard to the whole nanoparticle; the hydrophobic surface modifier is an water insoluble monomer, such as olefins, for example, polystyrene and the like, which weight percentage is 2-8% by weight with regard to the whole hydrophobic magnetic nanoparticle. The magnetic core particle is attached to its surface with an initiator such as 3-chloropropionic acid, and then a hydrophobic polymer based on styrenes is modified on the particle surface by a crosslinking agent via a chemical reaction such as radical, ring-opening polymerization and atom transfer radical polymerization (ATRP); the morphology of the particle may be spherical, rod-shaped and layered, preferably spherical particle. The crosslinking agent is 3-(methacryloyloxy) propyl triethoxysilane (MPS), divinylbenzene and diisocyanate or N,N-methylenebisacrylamide (MBA) and the like.

According to a third embodiment of the present invention, there is provided a photosensitive surface-modified functional particle, wherein the core has a size of 2-50 nm, and the magnetic core is 30-95% by weight with regard to the whole nanoparticle; the photosensitive modifier is selected from the group consisting of azos and quinolines as well as benzophenones (PVBP), etc., which weight percentage is 2-8% with regard to the whole hydrophobic magnetic nanoparticle. The magnetic core particle is attached to its surface with an initiator such as 3-chloropropionic acid, and then a photosensitive polymer based on benzophenone (PVBP) and the like is modified to the surface of the particle by a crosslinking agent via a chemical reaction such as radical, ring-opening polymerization and atom transfer radical polymerization (ATRP); the morphology of the particle may be spherical, rod-shaped and layered, preferably spherical particle. The crosslinking agent is 3-(methacryloyloxy) propyltriethoxysilane (MPS), divinylbenzene and diisocyanate or N,N-methylenebisacrylamide (MBA) and the like.

According to a fourth embodiment of the present invention, there is provided a thermosensitive surface-modified functional particle, wherein the size of the core is 2-50 nm, and the magnetic nano-core is 30-95% by weight with regard to the whole nanoparticle; the thermosensitive surface modifier is selected from the group consisting of amphiphilic polymers carrying amide bonds, such as polyacrylamide, poly N-substituted isopropylacrylamide, etc., which weight percentage is 2-8% with regard to the whole hydrophobic magnetic nanoparticle. The magnetic core particle is attached to its surface with an initiator such as 3-chloropropionic acid, and then a thermosensitive polymer such as poly N-substituted isopropylacrylamide is modified to the surface of the particle by a crosslinking agent via a chemical reaction such as radical, ring-opening assembly and atom transfer radical polymerization (ATRP); the shape of the particle may be spherical, rod-shaped and layered, preferably spherical particle. The crosslinking agent is 3-(methacryloyloxy) propyltriethoxysilane (MPS), divinylbenzene and diisocyanate or N,N-methylenebisacrylamide (MBA) and the like.

According to a fifth embodiment of the present invention, there is provided a pH-sensitive surface-modified functional particle, wherein the core has a diameter of 2 to 50 nm, the magnetic nano-core is 30 to 95% by weight with regard to the whole nanoparticle; the pH-sensitive surface modifier is selected from the group consisting of polymers carrying carboxyl groups and quaternary ammonium salt groups, such as polyacrylic acid, dimethylaminoethyl ester and dimethylaminopropyl methacrylate, etc., which weight percentage is 2-8% with regard to the whole hydrophobic magnetic nanoparticle. The magnetic core particle is attached to its surface with an initiator such as 3-chloropropionic acid, and then a pH-sensitive polymer based on dimethylaminoethyl methacrylate and dimethylaminopropyl methacrylate or the like is modified to the surface of the particle by a crosslinking agent via a chemical reaction such as radical, ring-opening polymerization and atom transfer radical polymerization (ATRP); the shape of the particle may be spherical, rod-shaped and layered, preferably spherical particle. The crosslinking agent is 3-(methacryloyloxy) propyltriethoxysilane (MPS), divinylbenzene and diisocyanate or N,N-methylenebisacrylamide (MBA) and the like.

In the above embodiments of the present invention, an initiator and/or a crosslinking agent are further included. The initiator includes thermal initiators, for example, potassium persulfate, ammonium persulfate and azo type initiators; the crosslinking agent includes 3-(methacryloyloxy) propyltriethoxysilane (MPS), divinylbenzene and diisocyanate or N,N-methylenebisacrylamide (MBA), molecular weight is 100,000, and oleic acid, etc.

According to a second aspect of the present invention, there is provided a preparation method for a nanoparticle. The preparation method generally includes two main steps: synthesis of a magnetic nanoparticle core, and various surface modifications based on the magnetic nanoparticle core (hydrophilic, hydrophobic and thermosensitive, photosensitive and pH-sensitive modification). Taking the preparation of magnetic Fe₃O₄ nanoparticles as an example, the two steps of the preparation method are respectively described in detail.

1) Preparation of Magnetic Fe₃O₄ Nanoparticle Core

FeCl₃.6H₂O and FeCl₂.4H₂O in a certain molar ratio (the molar ratio of FeCl₃.6H₂O and FeCl₂.4H₂O is 15% to 85%, preferably 1:2.5 to 1.5:1) are dissolved in 100 mL of water, fed with nitrogen gas to expel oxygen in the solution, added with aqueous ammonia at a room temperature of 20-30° C. to adjust the pH value of 8-12, preferably 10, and kept agitation and reaction for 20-40 minutes; then under a 50-100° C., preferably 70° C. water bath, the reaction is carried out for 20-40 minutes, and then Fe₃O₄ nanoparticles are obtained by separation with a magnet and drying. There are different kinds of preparation methods such as co-precipitation method, thermal decomposition method, hydrothermal synthesis method, microemulsion method (reverse micelle method) and the like.

2) Surface Modification of the Synthesized Fe₃O₄ Nanoparticle Core

2.1) Hydrophobic Modification of the Surface of the Synthesized Fe₃O₄ Nanoparticle Core

The Fe₃O₄ nanoparticle core prepared in the step 1) is dispersed into an aqueous solution, added with an initiator 3-chloropropionic acid and pre-treated for 12 hours, then added with an xylene solution of a hydrophobic surface-modifying monomer polystyrene and an active initiator CuCl and 4,4′-dinonyl-2,2-dipyridine (the molar ratio of the iron particle solution and the reaction solution is 1:1), and the mixture solution is reacted under continuous agitation at 130° C. for 15-30 hours, preferably 24 hours; the resulting nanoparticles are collected with a magnet and washed repeatedly with toluene to obtain the hydrophobic polystyrene-surrounded magnetic iron oxide nanoparticles.

Here, 3-chloropropionic acid is used as an initiator, and CuCl and 4,4′-dinonyl-2,2-bipyridine are used as another initiator. In addition, according to one embodiment of the present invention, the reaction time is preferably 18 to 30 hours, preferably 24 hours. In addition, according to one embodiment of the present invention, the solvent is toluene or xylene in an amount of ½ to 1 of the monomer volume, the mass ratio of the surface-modified polystyrene magnetic nanoparticles, the initiator and the monomer is 95:0.5:4.5.

2.2) Hydrophilic Modification of the Surface of the Synthesized Fe₃O₄ Nanoparticle Core

The Fe₃O₄ nanoparticle core obtained in the above step 1) is dissolved and dispersed into xylene, added with a silane coupling agent (the addition ratio of Fe₃O₄, nanoparticles and the silane coupling agent is 95:5), and reacted at 80° C. under nitrogen protection for 2-5 hours, preferably 3 hours; then washed with an alcoholic solvent (preferably absolute ethanol) and dried for 12 h, dispersed in an aqueous solution under ultrasonic condition, added with potassium persulfate; reacted under nitrogen protection at 40-80° C. for 10 minutes, then added with acrylic acid and reacted continuously at 40-80° C. for 1 hour, preferably reacted at a reaction temperature of 70° C.; separated by a magnet, washed and dried to obtain polyacrylic acid-modified, hydrophilic surface-modified magnetic nanoparticles.

Here, the silane coupling agent is 3-(methacryloyloxy)propyltriethoxysilane (MPS) in an amount of 8 to 16 times the mass of acrylic acid; the solvent is benzene or 2-toluene; potassium persulfate is used as initiator; the reaction time is preferably 20 minutes to 80 minutes. According to one embodiment of the present invention, the mass ratio of the surface-modified magnetic Fe₃O₄ nanoparticles, the potassium persulfate and the acrylic acid monomer is 25-100:1:100.

In addition, the alcoholic solvent here is methanol, ethanol or butanol, preferably ethanol, the reaction temperature is preferably 100° C. to 150° C., the reaction time is preferably 18 hours to 24 hours, and the mass ratio of the photosensitive monomer-modified magnetic nanoparticles, the potassium sulfate and the vinylbenzophenone monomer is 25-100:1:100.

2.3) Functional Modification of the Surface of the Synthesized Fe₃O₄ Nanoparticle Core

The Fe₃O₄ nanoparticle core as prepared in the above step 1) is dissolved and dispersed into xylene, added with a silane coupling agent (the addition ratio of the Fe₃O₄ nanoparticles and the silane coupling agent is 95:5), reacted under nitrogen protection at 80° C. for 2-5 hours, preferably 3 hours, then washed with an alcoholic solvent (preferably absolute ethanol) and dried for 12 hours, dispersed into an aqueous solution under ultrasonic condition, added with potassium persulfate; reacted under nitrogen protection at 40-80° C. for 10 minutes, then added with a photosensitive monomer vinyl benzophenone, or a thermosensitive monomer N-substituted isopropylacrylamide, or a pH-sensitive monomer dimethylaminoethyl methacrylate, reacted at 40-80° C. for 1 hour, preferably reacted at a reaction temperature of 70° C.; separated by a magnet, washed and dried to obtain magnetic nanoparticles with photosensitive, thermosensitive or pH-sensitive surface modification, respectively.

In addition, the functionally modified nanoparticles here may also be obtained by a cross-reaction with steps 2.1 and 2.2) and step 3) after pre-modification of the surface of the nanoparticle in the steps 2.1 and 2.2). That is, after the modification of 3-chloropropionic acid in step 2.1 (or the modification of silane coupling agent in step 2.2), the hydrophobic monomer styrene (or hydrophilic monomer acrylic acid) and the functional monomer such as vinyl benzophenone, N-substituted isopropylacrylamide or dimethylaminoethyl methacrylate and the like are added at the same time, and reacted at 40-80° C. for 1 hour, preferably reacted at a reaction temperature of 70° C.; separated by a magnet, washed and dried to obtain magnetic nanoparticles with photosensitive, thermosensitive or pH-sensitive surface modification. The co-reaction would result in co-modified functional nanoparticles corresponding to polystyrene (or polyacrylic acid) and the functional monomer.

Here, the silane coupling agent is 3-(methacryloyloxy)propyltriethoxysilane (MPS) in an amount of 8 to 16 times the mass of acrylic acid; the solvent is benzene or 2-toluele in an amount of 8 to 16 times the mass of acrylic acid; potassium persulfate is used as initiator; the reaction time is preferably 20 minutes to 80 minutes. According to one embodiment of the present invention, the mass ratio of the surface-modified magnetic Fe₃O₄ nanoparticles, the potassium persulfate and the acrylic acid monomer is 25-100:1:100.

In addition, the alcoholic solvent here is methanol, ethanol or butanol, preferably ethanol, the reaction temperature is preferably 100° C. to 150° C., and the reaction time is preferably 18 hours to 24 hours. The mass ratio of the functional monomer-modified magnetic nanoparticles, the potassium persulfate and the functional monomer is 25-100:1:100.

In the process for preparing the nano iron oxide (in step 1), the Fe₃O₄ nanoparticles are nanoscale ferroferric oxide particles (Fe₃O₄), MnFe₂O₄, nanoscale ferric oxide particles (γ-Fe₂O₃) or other nanoscale ferrite particles, the aqueous ammonia is used as catalyst, the reaction pH is preferably 9 to 10, the reaction time is preferably 20 to 30 minutes, the reaction temperature is between 50-100° C., preferably 70-80° C., the preferred ratio of Fe³⁺:Fe²⁺ is 15% to 85%, preferably 1.5:1 to 1:2.5.

In addition, in the above process for preparing nanoscale iron oxide (i.e., step 1)), the nanoparticle core is nanoscale ferroferric oxide particles (Fe₃O₄). Those skilled in the art can understand that it is also possible to use MnFe₂O₄, nanoscale ferric oxide particles (γ-Fe₂O₃) or other nanoscale ferrite particles. The aqueous ammonia is used as catalyst, the reaction pH is preferably 9 to 10, the reaction time is preferably 20-30 minutes, the reaction temperature is between 50-100° C., preferably 70-80° C. The preferred ratio of Fe³⁺:Fe⁺ is 15% to 85%, preferably 1:2.5 to 1.5:1.

In addition, in the above embodiments of the present invention, the agitation in the above reaction system is performed by a magnetic stirrer at a speed of 100-1000 revolutions/minute, preferably 500-700 revolutions/minute.

In addition, in the above embodiments of the present invention, the aqueous ammonia and the liquid monomer are added dropwise continuously and uniformly by an electronic pump at a rate of 20-100 drops/minute, preferably 40-60 drops/minute. Through the use of electronic pump for continuous and uniform dripping, large-scale production can be easily achieved, and the dispersibility and uniformity of nanoparticles can be well controlled.

According to a third aspect of the present invention, there is provided a magnetic probe rod system for assisting the removal of stone in urinary system. The magnetic probe rod system comprises a handle 1, a flexible rod 2, a magnetic field source 3, and an optional magnetically permeable material section 4 (in the present invention, the side of the handle is defined as the proximal end of the instrument, and the end of the magnetic field source is defined as the distal end). When an electromagnet is selected as the magnetic field source 3, a switch 11 can be integrated into the handle 1, and the magnetic field power supply can be selected from DC battery, and a battery compartment 12 a and a battery cover 13 a are provided accordingly; when an AC power is selected as the magnetic field power supply, an AC power plug 12 b is provided on the handle correspondingly. When the magnetic field source is an electromagnet, the magnetic field source 3 is composed of an electromagnet core 32 a and an electromagnetic coil 33 a, and externally provided with a magnetic field source encapsulation membrane 31 a made by biocompatible material; when the magnetic field source 3 is a permanent magnet, the magnetic field source 3 is composed of the permanent magnet 32 b and the magnetic field source encapsulation membrane 31 b on its surface; in order to ensure the accessibility of the present invention in human body, a magnetically permeable material section 4 can be optionally disposed at the distal end of the magnetic field source 3, that is, when the electromagnet is used as the magnetic field source, the magnetically permeable material section 4 a can be optionally disposed at the distal end of the electromagnet 3 a, and the magnetically permeable material section is composed of a highly magnetically permeable material 42 a and a magnetically permeable material encapsulating membrane 41 a, in which the highly magnetically permeable material 42 a can be made of an iron-based magnetically permeable material, preferably a pure iron material, and the magnetically permeable material encapsulating membrane 41 a and the magnetic field source encapsulation membrane 31 a can be made of the same material; when the permanent magnet is selected as the magnetic field source, the magnetically permeable material section 4 b may also be disposed at the distal end of the permanent magnet 3 b, composed of the highly permeable material 42 b and the magnetically permeable material encapsulation membrane 41 b, and the magnetically permeable material encapsulation membrane 41 b and the magnetic field source encapsulation membrane 31 b can be made of the same material; when it is not necessary to dispose a magnetically permeable material section at the distal end of the magnetic field source, the system of the present invention is composed of the handle 1, the flexible rod 2 and the magnetic field source 3; for example, when the permanent magnet is selected as the magnetic field source, the magnetic field source at distal end would be composed of a permanent magnet 32 c and an externally disposed magnetic field source encapsulation membrane 31 c; in the above embodiment, the flexible rod 2 may be made of a polymer material such as PU, TPU, PE, PVC, NYLON. PEBAX and silicone rubber, as well as modified materials of the above materials, and the magnetic field source encapsulation membranes 31 a, 31 b and 31 c as well as the magnetically permeable material encapsulation membranes 41 a and 41 b are all made of the same material as the flexible rods.

Further, the present invention provides an article comprising the magnetic nanoparticle, in which the magnetic nanoparticle is further processed to form a stone-removing solution (using physiological saline, buffer as solvent) or a stone-removing powder, preferably a stone-removing solution, which is used as a medical clinical article.

The basic principle of the high performance system for removing a stone in urinary system, which consists of the functional magnetic nanoparticle and the magnetic probe rod as shown, is achieved by the following steps: 1) pulverization of stones in vivo; 2) injection of the functional magnetic nanoparticles, the magnetic nanoparticles having excellent dispersibility (dispersibility and dispersion coefficient are related, the smaller the dispersion coefficient, the better the dispersibility); 3) interaction between the functional magnetic nanoparticles and the stones; 4) surrounding the stones with the functional magnetic nanoparticles (wherein, the surrounding stones is closely related to the dispersibility of the magnetic particles, the better the dispersibility and the better the effect of the surrounding stones); 5) physical or chemical crosslinking of the magnetic nanoparticles on the surface of the stones; 6) removal of the magnetized stones under the guidance of an external magnetic field (wherein, the effect of removing stones by guide is closely related to the effect of surrounding the stones, the better the effect of surrounding the stones, the better the effect of removing the stones). The stones are surrounded and magnetized by the magnetic nanoparticles via physical adsorption, chemical bonding and the like. The physical adsorption mainly refers to an attraction generated by van der Waal's force and hydrophobic interaction within the range of action between hydrophobic magnetic particles—particles and between particles—stones, so that the surface of the stones are adsorbed and surrounded by the magnetic particles; the chemical bonding mainly refers to the interaction between the hydrophilic magnetic nanoparticles—particles and between particles—stones mainly through the formation of chemical bonds (chemical bonds, such as hydrogen bonds, covalent bonds, etc., between carboxyl on the surface of the particles and the stones), so that the surface of the stones is surrounded with the magnetic particles; the chemical bonding includes: the functional magnetic nanoparticles (such as photosensitive, thermosensitive nanoparticles, etc.) firstly act on the stones via physical adsorption, and then further enhance the mutual force between particles—particles and particles—stones via photosensitive crosslinking, thermosensitive physical entanglement (crosslinking) and the like to surround the stones. The principle of the above interaction is shown in FIG. 15. In addition, during the modification process of the nanoparticles by the surface-modifier monomer, the dropping manner of the monomer for the surface-modifier monomer or the weight percentage of the shell formed by the monomer of the surface-modifier with regard to the nanoparticle has significant influences on the dispersibility, as shown in FIGS. 18-21.

The followings are detailed examples of the structure, preparation and use of the magnetic nanoparticles of the present invention.

Example 1: Preparation of Magnetic Nanoparticle Core

1. Preparation of 10 nm Fe₃O₄ by Co-Precipitation Method

3.05 g FeCl₃.6H₂O and 2.08 g FeCl₂.4H₂O (molar ratio 1:1) were dissolved in 50 ml deionized water in a three-necked flask. Nitrogen gas was used throughout the experiment. Aqueous ammonia was added dropwise with a syringe and stirred vigorously at room temperature to adjust pH to 9, the solution gradually turned from yellow to brown and finally black, and the reaction was carried out for 20 minutes. After the reaction, the solution was placed in a 70° C. water bath and incubated for 20 minutes, stirred vigorously to remove excess ammonia. The three-necked flask was taken out and allowed to cool to room temperature under vigorous agitation. The suspension of the synthesized Fe₃O₄ magnetic particles was poured into a 50 ml centrifuge tube, a powerful magnet was used to attract the magnetic particles, liquid waste was discarded, deionized water was added, the magnetic particles were re-suspended under ultrasonic, so repeatedly to wash away excess ammonia until pH showed neutral. The collected magnetic particles were placed in an oven at 65° C. to be dried and dewatered. The synthesized magnetic particles were weighed, and 1.0 ml suspension of 0.02 mg/ml magnetic particles was formulated for measurement of particle size. A total of 1.5 ml of 0.02M sodium oleate solution was added dropwise to 1.0 ml suspension of 0.2 mg/ml magnetic particles, reacted at 70° C. under nitrogen and vigorous agitation for 30 minutes, and then cooled to room temperature. Excess sodium oleate was removed by dialysis using 12 KD dialysis membrane. Thus, 1.0 ml of 0.02 mg/ml sodium oleate-encapsulated Fe₃O₄ solution was formulated, and its particle size was measured.

2. Preparation of Fe₃O₄ Magnetic Nanoparticle Core

2.1 Thermal Decomposition Method

2.1.1 Synthesis of 4 nm Fe₃O₄ Seeds:

5 mmol of ferric triacetylacetonate, 5 mmol of 1,2-dihydroxyhexadecane, 3 mmol of oleic acid, 1 mmol of oleylamine were dissolved in 20 ml of diphenyl ether and magnetically stirred under a nitrogen atmosphere. The above mixture was stirred at 200° C. for 30 minutes, and then heated under reflux for 30 minutes at 265° C. under the protection of nitrogen gas. The heating was stopped, and the dark brown liquid mixture obtained from the reaction was cooled to room temperature under atmospheric conditions, 400 ml of ethanol was added, and the resulting black material was separated by overspeed centrifugation. The black product obtained by centrifugation was redissolved in n-hexane containing 50 μL of oleic acid and 50 μL of oleylamine, centrifuged at 600 rpm for 10 minutes to remove insoluble residues. The resulting 4 nm Fe₃O₄ product was precipitated with ethanol, centrifuged at 600 rpm for 10 minutes to remove solvent and then redispersed into n-hexane. The following different methods were used respectively to synthesize surface-functionalized nanoparticles with different sizes.

2.1.2 Synthesis of 6 nm Fe₃O₄ Nanoparticle Core Using 4 nm Fe₃O₄ Seeds

20 mmol of ferric triacetylacetonate, 10 mmol of 1,2-dihydroxyhexadecane, 6 mmol of oleic acid and 6 mmol of oleylamine were dissolved in 20 ml of diphenyl ether and magnetically stirred under a nitrogen atmosphere. The above mixture was heated at 200° C. for 2 hours, and then heated under reflux for 1 h at 300° C. under the protection of nitrogen gas. The heating was stopped, and the dark brown liquid mixture obtained from the reaction was cooled to room temperature. The aforementioned operation steps for the synthesis of the 4 nm Fe₃O₄ particles were adopted to obtain a black brown suspension of 6 nm Fe₃O₄ particles dispersed in n-hexane.

2.1.3 Synthesis of 8 nm Fe₃O₄ Nanoparticle Core Using 6 nm Fe₃O₄ Seeds

2 mmol of ferric triacetylacetonate, 10 mmol of 1,2-dihydroxyhexadecane, 2 mmol of oleic acid and 2 mmol of oleylamine were dissolved in 20 ml of ethyl ether and magnetically stirred under nitrogen protection. 84 mg of 6 nm Fe₃O₄ particles were weighed, dissolved in 4 ml of n-hexane, and then added to the above mixture liquid. The above mixture liquid was first heated at 100° C. for 30 minutes to remove n-hexane, then heated at 200° C. for 1 hour, and heated under reflux at 300° C. for 30 minutes under nitrogen protection. The heating was stopped, and the black mixture liquid resulting from the reaction was allowed to cool to room temperature. The aforementioned synthesis steps for 4 nm Fe₃O₄ particles was used to give a dark brown suspension of 8 nm Fe₃O₄ particles dispersed in n-hexane. Similarly, 80 mg of 8 nm Fe₃O₄ seeds reacted with 2 mmol of ferric triacetylacetonate and 10 mmol of 1,2-dihydroxyhexadecane to produce 10 nm Fe₃O₄ nanoparticles. Using this Fe₃O₄ seed-mediated growth method, Fe₃O₄ nanoparticles with larger size (up to 20 nm) could be synthesized.

2.1.4. Surface Modification of Fe₃O₄ Nanoparticle Core

Under atmospheric conditions, 200 μl of n-hexane solvent with 20 mg of dispersed hydrophobic Fe₃O₄ nanoparticle core was added to 2 ml of dichloromethane suspension containing 20 mg of tetramethylammonium salt of 1-aminoundecanoic acid. The mixture was shaken for 20 minutes, while a magnet was used to separate the precipitated Fe₃O₄ nanoparticles. The solvent and the non-magnetic suspended matter were decanted, the resulting precipitate was washed once with dichloromethane, and then the separation with magnet was performed again to remove excess surfactant. The resulting product was dried under nitrogen gas and then dispersed in deionized water or pH-neutral PBS.

2.2 Hydrothermal Synthesis Method

1.35 g (5 mmol) of ferric chloride hexahydrate (FeCl₃.6H₂O) was dissolved in 40 mL of ethylene glycol to form a clear solution. To the above solution, 3.6 g of sodium acetate and 1.0 g of polyethylene glycol were added, stirred vigorously for 30 minutes, and then transferred to a 50 ml sealed stainless steel autoclave, reacted at 200° C. for 8-72 hours, and then cooled to room temperature. The black product obtained in the reaction was washed with ethanol for several times and then dried at 60° C. for 6 hours, to obtain a magnetic nanoparticle core having a particle diameter of 10 nm or less.

2.3 Microemulsion Method (Reverse Micellar Method)

5 mmol of Mn(NO₃)₃ and 10 mmol of Fe(NO₃)₃ were dissolved in 25 mL of deionized water to form a clear and transparent solution; 25 mL of 0.4 M NaDBS ([CH₃(CH₂)₁₁(C₆H₄)SO₃]Na) was added to the above iron ion solution, and then added with a large volume of toluene, in which the particle size of the resulting MnFe₂O₄ nanoparticles depended on the volume ratio of water and toluene. For example, in order to obtain 8 nm nanoparticles, the volume ratio of water and toluene should be 5:100. After the above mixture liquid was stirred overnight, it became a clear single-phase solution containing reversed micelles.

In order to form colloids in the reversed micelles, 40 mL of 1 M NaOH solution was added dropwise with vigorous stirring, and the stirring was continued for 2 hours. The water and most of the toluene in the solution were removed by distillation to reduce the volume of the solution. The resulting concentrated solution containing suspended colloids was washed with water and ethanol to remove excess surfactant in the solution. A primary magnetic nanoparticle core was obtained by ultracentrifugation, and a nanocrystal was obtained by heating at 350° C. under nitrogen atmosphere for 12 hours.

Example 2: Hydrophobic Polystyrene Surface Modification

(Modification on the Magnetic Nanoparticle Core (MnFe₂O₄) Obtained in Example 1)

MnFe₂O₄ nanoparticles with an average particle size of 9 nm were added to an aqueous solution/3-chloropropionic acid solution with a concentration of 1.0 mol/L initiator, the solution was adjusted to pH of 4 with hydrochloric acid, and stirred overnight. The nanoparticles were collected with a magnet, washed with water for several times to remove excess 3-chloropropionic acid. 0.22 g of dried nanoparticles were added to 8 mL of polystyrene solution under continuous feeding of nitrogen gas, followed by the addition of 4 mL of an xylene solution of 0.3 mmol of CuCl and 1.1 mmol of 4,4′-dinonyl-2,2-dipyridine. The above mixture reacted at 130° C. for 24 h under continuous agitation. The nanoparticles were collected with a magnet and washed repeatedly with toluene to obtain polystyrene-surrounded magnetic iron oxide nanoparticles.

Example 3: Hydrophilic Polyacrylic Acid Modification

1 g of Fe₃O₄ obtained in Example 1 (for example, 10 nm Fe₃O₄ obtained by co-precipitation method) and 5 ml of a silane coupling agent (methacryloxypropyltrimethoxysilane, KH570) were mixed with 50 ml of xylene in a reaction flask. Under nitrogen protection, the reaction was carried out under stirring at 80° C. for 3 hours. After the reaction, the mixture was centrifuged and washed with ethanol three times to remove the silane coupling agent adsorbed on the surface of the Fe₃O₄, and vacuum-dried for 12 hours. The above-mentioned silane coupling agent-activated Fe₃O₄, 40 mg of potassium persulfate and 30 ml of deionized water were added in a flask, reacted under under nitrogen protection and stirring at 40° C. for 10 minutes. Then, 4 ml of acrylic acid was slowly dropped into the flask, and reacted under nitrogen protection and stirring al 3) 40° C. for 1 hour. The nanoparticles were magnetically separated, washed three times with deionized water and finally dried under vacuum.

Example 4: Photosensitive Functional Modification of Nanoparticles

1. Synthesis of Photosensitive Functional Monomer

The synthesis method of photosensitive monomer with photo-crosslinking characteristics comprised: 4-vinylbenzophenone (4VBP) and styrene monomer were directly polymerized by atom transfer radical polymerization (ATRP) to obtain a photosensitive polystyrene-polyvinylbenzophenone copolymer (PS-PVBP), wherein the specific steps were as follows: in a dry Schlenk tube connected with a reflux condenser, Cu(I)Br (0.695 mg, 4.8 umol), 4VBP (1.0 g, 4.8 mmol), styrene (2 u, 20 umol) and 4-vinylbenzophenone (1 μL, 4.8 umol) were added, and the mixture was degassed for three times by means of freeze-pump-thaw circulation. Methyl bromopropionate (5.35 μL, 48 umol) was added to the above mixture at −78° C. under condition of nitrogen with positive pressure, and the mixture was degassed again for three more times by means of freeze-pump-thaw circulation. Polymerization was carried out by heating the mixture to a temperature of 85° C. under negative pressure, and the reaction was allowed to proceed for 4 hours. The above Schlenk tube was immersed in liquid nitrogen, and 10 ml of dichloromethane was added to dissolve the polymer. The resulting solution was precipitated twice with methanol (2×300 mL) to give PS_(x)-PVBP_(y) as a light yellow solid, wherein x: y˜(60%-90%), and a preferred composition was PS₇₅-PVBP₂₅. In the same way, PS₇₅-PVBP₂₅-PAA₁₀₀ could be obtained by adding hydrophilic monomer acrylic acid.

2. Preparation of Nanoparticles Surrounded with Photosensitive Cross-Linked Micelles

(Polystyrene₇₅-co-polyvinylbenzophenone₂₅)-polyacrylic acid₁₀₀, namely (PS₇₅-co-PVBP₂₅)₁₁₅-b-PAA₁₀₀, was chosen as a polymer to form micelles in aqueous solution. 5 mg of (PS₇₅-co-PVBP₅₂)₁₁₅-b-PAA₁₀₀ and 10 mg of Fe₃O₄ obtained in Example 1 (for example, 10 nm Fe₃O₄ obtained by co-precipitation method) were dissolved in 10 ml of dimethylformamide (DMF) solution; and then double distilled water (0.1 ml/min) was gradually added under vigorous stirring. When the volume of water reached 60%, the resulting solution was added to a dialysis membrane with a molecular weight cut off of 12K-14K and dialyzed against water for 24 hour to remove DMF, and then the micellar solution was transferred to a quartz tube and irradiated with a laser at different time periods (emission wavelength: 315-400 nm) to form a photosensitive monomer-surrounded nanoparticle.

Example 5: Thermosensitive Functional Modification of Nanoparticles

1 g of Fe₃O₄ obtained in Example 1 (for example, 10 nm Fe₃O₄ obtained by co-precipitation method) and 5 ml of a silane coupling agent (methacryloxypropyltrimethoxysilane, KH570) were mixed with 50 ml of xylene in a reaction flask. Under nitrogen protection, the reaction was carried out with stirring at 80° C. for 3 hours. After the completion of the reaction, the mixture was centrifuged and washed with ethanol three times to remove the silane coupling agent adsorbed on the surface of the Fe₃O₄, and vacuum-dried for 12 hours. The above-mentioned silane coupling agent-activated Fe₃O₄, 40 mg of potassium persulfate and 30 ml of deionized water were added in a flask, reacted under nitrogen protection and stirring at 40° C. for 10 minutes. Then, 4 ml of N-isopropylacrylamide aqueous solution was slowly dropped into the flask, and reacted under nitrogen protection and stirring at 40° C. for 1 hour. The nanoparticles were magnetically separated, washed three times with deionized water and finally dried in vacuo.

Example 6: pH-Sensitive Functional Modifications of Nanoparticles

1 g of Fe₃O₄ obtained in Example 1 (for example, 10 nm Fe₃O₄ obtained by co-precipitation method) and 5 ml of a silane coupling agent (methacryloxypropyltrimethoxysilane, KH1570) were mixed with 50 ml of xylene in a reaction flask, and reacted under nitrogen protection and stirring at 80° C. for 3 hours. After the completion of the reaction, the mixture was centrifuged and washed with ethanol three times to remove the silane coupling agent adsorbed on the surface of the Fe₃O₄, and dried in vacuo for 12 hours. The above-mentioned silane coupling agent-activated Fe₃O₄, 40 mg of potassium persulfate and 30 ml of deionized water were added in a flask, reacted under nitrogen protection and stirring at 40° C. for 10 minutes. Then, 4 ml of dimethylaminoethyl methacrylate aqueous solution was slowly dropped into the flask, and reacted at 40° C. for 1 hour under stirring and nitrogen protection. The nanoparticles were magnetically separated, washed three times with deionized water and finally dried in vacuo.

Example 7: Biocompatibility Evaluation

Cell Plating: 293t cells in logarithmic growth phase were digested, counted after centrifugation, and plated on a 96-well plate with a cell density of 5.0×10⁴/well. 100 μl of serum-containing medium was added to each well. The surrounding blank wells were each complemented with 100 μl of serum-containing medium. The plate was placed in a 7% CO₂, 37° C. cell incubator overnight. The hydrophilically modified magnetic nanoparticles of Example 3 in an amount of 100 μl per well were added to the cell wells and incubated with N87 cells, wherein the magnetic nanoparticles obtained in Example 3 was used in concentrations of 0.1, 0.2, 0.4, 0.8, 1.0 mg/ml respectively. After incubated at 37° C. for 24 hours, the cells were gently washed twice with culture medium, and then the cell viability was measured with a Cell Counting Kit-8 kit, in which the detection conditions were as follows: 10 μl of CCK-8 reagent per well, incubate at 37° C. for 2 hours, read the absorbance value at 450 nm with BIO-TEK ELx800 automatic microplate reader, and calculate the cell viability. The results shown in FIG. 5, indicating the synthesized hydrophilically modified magnetic nanoparticles had good biocompatibility and almost no toxicity in vivo, and giving preliminary evidences of applicability for in vivo experiments.

Example 8: Evaluation of In Vitro Stone Separation with Assistance of Nanoparticles

As shown in FIG. 6, a certain amount of stones were weighed, pulverized with a pestle into a powder (particle size 0.5-2 mm), poured into a transparent glass bottle, and PBS solution was added to obtain a stone liquid. After being mixed uniformly, the hydrophilically modified magnetic particles of Example 3 at a concentration of 1 mg/ml was used as a separation liquid and added, and then gently shaken. After standing for 5 minutes, separation was carried out with a magnet. During standing, it was observed that the color of the mixture gradually faded, and after 5 minutes, it was observed that the black magnetic particles were adsorbed on the surface of the stone. Under the guidance of the magnetic field, the stones with magnetic particles adsorbed on their surface moved toward the magnet.

Example 9: Evaluation of In Vive Safety of Nanoparticles in Animals

As shown in FIG. 7, one 6-week-old nude rat and 3 mice were intraperitoneally injected and tail vein injected, respectively. The hydrophilically modified magnetic nanoparticles of Example 3 at a concentration of 0.5 mg/ml and in an amount of 200 μL were used for the injection for consecutive two days. The living conditions of the mice were observed periodically (such as one week, two weeks, etc.). The results showed that after intravenous injection of 200 μL of magnetic nanoparticle solution, no obvious toxicity was found in the nude rat and the mice within 1 week; and after intraperitoneal injection of particle solution at the same concentration 3 times, it was found that the rat and the mice had good survival status within 3 months. This shows that the prepared magnetic nanoparticles have good biocompatibility, and such preliminary assessment shows they basically have no acute toxicity and chronic toxicity.

Example 10: Using Magnetic Nanoparticles in Removal of Urinary Stones

In the treatment of disease of kidney stones, an ureteroscope was used for holmium laser lithotripsy. In the operation, after crushing process of kidney stones with holmium laser, 200 ml of the hydrophilic magnetic nanoparticle solution of Example 3 according to the present invention was injected into the kidney through the working channel of the ureteroscope, so that the hydrophilic magnetic nanoparticle solution was thoroughly mixed with the stone debris. After about 3 minutes, the nanoparticles in the solution completely adhered to the surface of the stone debris, and magnetized the stone debris. The above-mentioned magnetic probe rod system for removal of stones in urinary system, in which a NdFeB permanent magnet was used as the magnetic field source 3, was inserted into the kidney through the working channel of the ureteroscope. Under the action of the magnetic field at the distal end of the magnetic probe rod system, the magnetized stone debris moved closer to the distal end of the magnetic probe rod and attracted to the magnetic probe rod. Finally, the magnetic probe rod system filled with stones debris at its distal end together with the ureteroscope were drawn from the body through the soft sheath of the ureteroscope. After the the stone debris were removed from the distal end of the magnetic probe rod, the magnetic probe rod could be inserted again into the endoscope to carry out stone removal operation, until all of the stone debris inside the kidney were removed from the body. In this Example, the stone had a diameter of about 20 mm and was located in the lower kidney calyx. By using the magnetic probe rod system in combination with the hydrophilic magnetic nanoparticle material of the present invention, all (100%) of the stone debris were removed from the body. In comparison with the traditional method of removing stones by baskets and the method of pulverizing stones and then allowing patients to discharge stone debris, the technical solutions of the present invention achieved simple, efficient and complete removal of stones, thereby greatly improving the efficiency and safety of stone removal operations.

Example 11: Effect of the Mode of Dropping Surface Modifier Monomer on the Dispersibility of Magnetic Nanoparticles

1 g of Fe₃O₄ obtained in Example 1 (for example, 10 nm Fe₃O₄ obtained by co-precipitation method), 5 ml of a silane coupling agent (methacryloxypropyltrimethoxysilane, KH570) were mixed with 50 ml of xylene in a reaction flask. Under nitrogen protection, the reaction was carried out under stirring at 80° C. for 3 hours. After the completion of the reaction, the mixture was centrifuged and washed with ethanol three times to remove the silane coupling agent adsorbed on the surface of the Fe₃O₄, and vacuum-dried for 12 hours. The above-mentioned silane coupling agent-activated Fe₃O₄, 40 mg of potassium persulfate and 30 ml of deionized water were added in the flask, stirred and reacted under protection at 40° C. for 10 minutes.

In order to compare the influence of the mode of dropping the surface modifier monomer (taking acrylic acid as the representative) on the particle dispersibility of the final magnetic nanoparticles, the experiments were carried out to systematically compare the dropping group (manual and gradual dropping of acrylic acid surface-modifier monomer) and the continuous addition group (electronic and continuous dropping of acrylic surface-modifier monomer). In the dropping group, 4 ml of acrylic acid for manual and gradual dropping was gradually dropped (every 3 seconds) by hand using an injection syringe into the flask, and the reaction was carried out under nitrogen protection and stirring at 40° C. for 1 hour. In the continuous addition group, 4 ml of acrylic acid for electronic and continuous dropping was added dropwise and uninterruptedly by an electronic pump at the designed speed to the flask, and the reaction was carried out under nitrogen protection and stirring at 40° C. for 1 hour. Finally, the nanoparticles were magnetically separated, washed three times with deionized water and finally dried under vacuum.

Using the German ALV-CGS3 static and dynamic laser light scattering instrument, the monodispersity coefficient of the magnetic nanoparticles was measured, and the specific experimental results were shown in FIG. 18. It can be seen from FIG. 18 that, in comparison with the monodispersity coefficient (0.478±0.075) of the magnetic nanoparticles of the dropping group, the monodispersity coefficient (0.0043±0.0016) of the magnetic nanoparticles of the continuous addition group was far lower, that is, the magnetic nanoparticles obtained in the continuous addition group have better dispersibility.

Further, it can be seen from FIGS. 19-20 that the dispersibility of the magnetic nanoparticles of the continuous addition group was better than that of the magnetic nanoparticles of the dropping group.

Example 12: Effect of the Weight Percentage of the Nanoparticle Shell with Regard to the Nanoparticles on the Dispersibility of the Nanoparticles

1 g of Fe₃O₄ obtained in Example 1 (for example, 10 nm Fe₃O₄ obtained by co-precipitation method) and 5 ml of a silane coupling agent (methacryloxypropyltrimethoxysilane, KH570) were mixed with 50 ml of xylene in a reaction flask. Under nitrogen protection, the reaction was carried out under stirring at 80° C. for 3 hours. After the completion of the reaction, the mixture was centrifuged and washed with ethanol three times to remove the silane coupling agent adsorbed on the surface of the Fe₃O₄, and vacuum-dried for 12 hours. The above-mentioned silane coupling agent-activated Fe₃O₄, 40 mg of potassium persulfate and 30 ml of deionized water were added in a flask, stirred and reacted at 40° C. for 10 minutes under protection of nitrogen atmosphere.

In order to compare the influence of the weight percentage of the shell formed by the surface-modifier monomer (taking acrylic acid as representative) on the surface of the nanoparticles on the dispersibility of the final particles, the nanoparticle dispersibilities of the nanoparticles of the following 6 groups were systematically compared: Group 1 (the weight percentage of the shell is 0.5%, with regard to the weight of the particles), Group 2 (the weight percentage of the shell is 1%, with regard to the weight of the particles), Group 3 (the weight percentage of the shell is 2%, with regard to the weight of the particles), Group 4 (the weight percentage of the shell is 15%, with regard to the weight of the particles), Group 5 (the weight percentage of the shell is 40%, with regard to the weight of the particles) and Group 6 (the weight percentage of the shell is 45%, with regard to the weight of the particles). In the experiment, the aqueous solution of acrylic acid for each of the weight percentage groups was slowly dropped into the flask, and reacted under nitrogen protection and stirring at 40° C. for 1 hour. The nanoparticles were magnetically separated, washed three times with deionized water and finally dried in vacuo.

The monodispersity coefficient of the magnetic nanoparticles was measured by the German ALV-CGS3 dynamic and static laser light scattering instrument, and the specific experimental results were as follows: the monodispersity coefficient of the nanoparticles of Group 1 was 0.5±0.04; the monodispersity coefficient of the nanoparticles of Group 2 was 0.026±0.0026; the monodispersity coefficient of the nanoparticles of Group 3 was 0.036±0.003; the monodispersity coefficient of the nanoparticles of Group 4 was 0.022±0.002; the monodispersity coefficient of the nanoparticles of Group 5 was 0.031±0.0028; the monodispersity coefficient of the nanoparticles of Group 6 was 0.58±0.05.

The above experimental results show that, compared with the monodispersity coefficients of the nanoparticles in the groups (Groups 1 and 6) wherein the shell weight percentages were 0.5% and 45% with regard to the nanoparticles, respectively, the monodispersity coefficients of the nanoparticles in the groups (Groups 2, 3, 4 and 5) wherein the shell weight percentages were 1%, 2%, 15% and 40% with regard to the nanoparticles were much lower (see FIG. 21), that is, the nanoparticles of Groups 2, 3, 4 and 5 have better dispersibility.

While many embodiments of the invention have been shown and/or discussed herein, it is not intended that the invention is limited thereto. It is anticipated that the scope of the present invention will be the same as what is allowed in the art, and equally appreciated according to the description. Therefore, the above description should not be construed as limiting, but merely as exemplifications of specific embodiments. Those skilled in the art can envision other variations within the scope and spirit of the claims appended hereto. 

What is claimed:
 1. A nanoparticle, the nanoparticle comprises: a nanoparticle core made of a magnetic material; and a nanoparticle shell formed by in-situ modification of a surface modifier monomer to the surface of the nanoparticle core with an initiator and/or a crosslinking agent; wherein the surface of the nanoparticle after surface modification and functionalization has an amide bond or a carboxyl group, and the weight percentage of shell is 0.5-45% (excluding end points), with regard to the weight of the nanoparticle.
 2. The nanoparticle according to claim 1, wherein the weight percentage of shell is 1-40%, more preferably 2-40%, further more preferably 1-15%, much further more preferably 2-15%, most preferably 1%, 2%, 15% or 40%, with regard to the weight of the nanoparticle.
 3. The nanoparticle according to claim 1, wherein the nanoparticle core has a diameter of 2-50 nm, and a weight percentage of 30-95% with regard to the whole weight of the nanoparticle, and its magnetic material includes a compound of Fe³⁺, Fe²⁺, Mn²⁺, Ni²⁺, or a metal element selected from iron, nickel, copper, cobalt, platinum, gold, europium, gadolinium, dysprosium, terbium, or a composite or oxide of the aforementioned metals, or any one of the above items or a combination of two or more of the above items, preferably Fe³⁺, Fe²⁺, Mn²⁺, Ni²⁺ compounds, more preferably Fe³⁺ and Fe²⁺ in a ratio of 15% to 85%, preferably 1:2.5 to 1.5:1.
 4. The nanoparticle according to any one of claims 1-3, wherein the surface modifier includes a hydrophilic surface modifier, a hydrophobic surface modifier, a photosensitive, a thermosensitive surface modifier or a pH sensitive surface modifier with function response, wherein the hydrophilic surface modifier includes acrylic acid, methacrylic acid, isobutyl acrylamide or poly N-substituted isopropylacrylamide; the hydrophobic surface modifier includes olefins, preferably polystyrene, polyethylene or oleic acid; the photosensitive surface modifier is selected from the group consisting of azos and quinolines and benzophenones (PVBP), preferably vinyl benzophenone; the thermosensitive surface modifier is selected from the group consisting of amphiphilic polymers with an amide bond, preferably polyacrylamide or poly N-substituted isopropylacrylamide; the pH-sensitive surface modifier is selected from the group consisting of polymers with a carboxyl group and a quaternary ammonium salt, preferably polyacrylic acid, dimethylaminoethyl ester and dimethylaminopropyl methacrylate; the particle is of spherical shape, rod shape or diamond shape.
 5. The nanoparticle according to any one of claims 1-3, wherein the crosslinking agent includes 3-(methacryloyloxy)propyltriethoxysilane, divinylbenzene, diisocyanate or N,N-methylenebisacrylamide, and the initiator includes 3-chloropropionic acid, CuCl, 4,4′-dinonyl-2,2-bipyridine or potassium persulfate.
 6. A nanoparticle, the nanoparticle comprises: a nanoparticle core made of a magnetic material; and a nanoparticle shell formed by in-situ modification of a surface modifier monomer to the surface of the nanoparticle core with an initiator and/or a crosslinking agent; wherein the surface of the nanoparticle after surface modification and functionalization has an amide bond or a carboxyl group, and the method for preparing the magnetic nanoparticle core is co-precipitation method, wherein the mode of adding the surface modifier monomer is a continuous dropping with assistance of an electronic pump.
 7. The nanoparticle according to claim 6, wherein the nanoparticle core has a diameter of 2-50 nm, and a weight percentage of 30-95% with regard to the whole weight of the nanoparticle, and its magnetic material includes a compound of Fe³⁺, Fe²⁺, Mn²⁺, Ni²⁺, or a metal element selected from iron, nickel, copper, cobalt, platinum, gold, europium, gadolinium, dysprosium, terbium, or a composite or oxide of the aforementioned metals, or any one of the above items or a combination of two or more of the above items, preferably Fe³⁺, Fe²⁺, Mn²⁺, Ni²⁺ compounds, more preferably Fe³⁺ and Fe²⁺ in a ratio of 15% to 85%, preferably 1:2.5 to 1.5:1.
 8. The nanoparticle according to claim 7, wherein the mutual forces for surrounding and crosslinking between the nanoparticles and the stone include: van der Waal's force that form an interacting surrounding, hydrophobic interaction, adsorption and surface deposition; chemical bonds formed between carboxyl-stone, including hydrogen bonds, ester bonds, amide bonds and other covalent bonds; interacting physical and chemical entanglements between chains and chemical crosslinking between chains.
 9. The nanoparticle according to any one of claims 6-8, wherein the surface modifier includes a hydrophilic surface modifier with function response, a hydrophobic surface modifier with function response, a photosensitive surface modifier with function response, a thermosensitive surface modifier with function response or a pH sensitive surface modifier with function response, wherein the hydrophilic surface modifier includes acrylic acid, methacrylic acid, isobutyl acrylamide or poly N-substituted isopropylacrylamide; the hydrophobic surface modifier includes olefins, preferably polystyrene, polyethylene or oleic acid; the photosensitive surface modifier is selected from the group consisting of azos and quinolines and benzophenones (PVBP), preferably vinyl benzophenone; the thermosensitive surface modifier is selected from the group consisting of amphiphilic polymers with an amide bond, preferably polyacrylamide or poly N-substituted isopropylacrylamide; the pH-sensitive surface modifier is selected from the group consisting of polymers with a carboxyl group and a quaternary ammonium salt, preferably polyacrylic acid, dimethylaminoethyl ester and dimethylaminopropyl methacrylate; the shell accounts for 0.5-45% by weight (excluding end points) of the nanoparticle, preferably 1-40%, more preferably 2-40%, further more preferably 1-15% or 2-15%, most preferably 1%, 2%, 15% or 40%; preferably, the particle is of spherical shape, rod shape or diamond shape.
 10. The nanoparticle according to any one of claims 6-9, wherein the crosslinking agent includes 3-(methacryloyloxy)propyltriethoxysilane, divinylbenzene, diisocyanate or N,N-methylenebisacrylamide, and the initiator includes 3-chloropropionic acid, CuCl, 4,4′-dinonyl-2,2-bipyridine or potassium persulfate.
 11. A method for preparing the nanoparticle according to any one of claims 1-10, wherein said method includes the following steps: a) preparing the nanoparticle core using the magnetic material; b) forming the nanoparticle shell by in-situ linking the surface modifier monomer to the nanoparticle core by the initiator and/or crosslinking agent, thereby forming the nanoparticle.
 12. The method according to claim 11, wherein the magnetic material includes a compound of Fe³⁺, Fe²⁺, Mn²⁺, Ni²⁺, or a metal element selected from iron, nickel, copper, cobalt, platinum, gold, europium, gadolinium, dysprosium, terbium, or a composite or oxide of the aforementioned metals, or any one of the above items or a combination of two or more of the above items, preferably Fe₃O₄, MnFe₂O₄, γ-Fe₂O₃ or other nanoscale sized ferrite particles, more preferably FeCl₃.6H₂O and FeCl₂.4H₂O in a molar ratio of 15% to 85%, preferably 1:2.5 to 1.5:1, including the following steps: dissolving a proportion of the metal salt-containing material in water; feeding nitrogen to expel oxygen in the solution; adding a catalyst at a room temperature of 10-40° C., preferably 30° C., to adjust the pH to 7-12, preferably 10; keeping agitation and reaction for 10-60 minutes; and reacting under condition of 40-100° C., preferably 70° C. water bath, for 20-40 minutes, then separating with a magnet and drying to obtain the magnetic nanoparticle core.
 13. The method according to claim 12, wherein when aqueous ammonia is used as the catalyst to prepare the nanoparticle, the method for dropping the aqueous ammonia is performed in a continuous and dropwise manner with assistance of an electronic pump at a speed of 20-100 drops/minute, preferably 40-60 drops/minute; and when the magnetic material is a liquid monomer material, the liquid monomer is added in a dropwise and continuous manner with assistance of an electronic pump, and the reaction is carried out under agitation with a speed of 100-1000 revolutions/minute, preferably 500-700 revolutions/minute.
 14. The method according to any one of claims 11-13, wherein said method further includes hydrophobic surface modification based on the obtained nanoparticle core, including steps of: dispersing the prepared nanoparticle core in an aqueous solution, and adding with an xylene solution of 3-chloropropionic acid, polystyrene, CuCl and 4,4′-dinonyl-2,2-bipyridine, wherein the molar ratio between the solution of the nanoparticle core and the reaction solution is 1:1; reacting the mixture at 130° C. under continuous agitation for 15-30 hours, preferably 24 hours; and collecting the nanoparticles with a magnet, washing repeatedly with toluene to obtain hydrophobic polystyrene-surrounded magnetic iron oxide nanoparticles.
 15. The method according to any one of claims 11-13, wherein said method further includes hydrophilic surface modification based on the obtained nanoparticle core, including steps of: dispersing the prepared nanoparticle core in xylene, and added with a silane coupling agent, wherein the nanoparticles, xylene and silane coupling agent are added in a ratio of 95:5; reacting under nitrogen protection at 20-100° C., preferably at 80° C., for 2-5 hours, preferably for 3 hours; washing with an alcoholic solvent and drying for 12 hours, dispersing in an aqueous solution under ultrasonic condition, adding with potassium persulfate; reacting under nitrogen protection at 40-80° C. for 10 minutes, then adding with acrylic acid to continue reaction at 40-80° C. for 1 hour, preferably at the reaction temperature of 70° C.; and magnetically separating, washing and drying to obtain the polyacrylic acid-modified hydrophilic nanoparticle.
 16. The method according to any one of claims 11-13, wherein said method further includes performing a photosensitive, thermosensitive and pH-sensitive surface modification based on the resulting nanoparticle core or on a hydrophilic surface thereof, or performing a hydrophilic, hydrophobic, light-sensitive, thermosensitive, pH-sensitive co-modification based on the nanoparticle core, wherein the re-modification on the hydrophilic surface includes the steps of: dissolving and dispersing the polyacrylic acid-modified magnetic nanoparticle in an alcoholic solvent, adding with a photosensitive monomer such as vinylbenzophenone, a thermosensitive monomer such as N-isopropylacrylamide, or a pH-sensitive monomer such as dimethylaminopropyl methacrylate or a blend monomer of acrylic acid and styrene, continuously reacting at 40-80° C. for 1 hour, preferably at a reaction temperature of 70° C.; and magnetically separating, washing and drying to obtain a photosensitive, thermosensitive or pH-Sensitive functional monomer-modified magnetic nanoparticle.
 17. A stone removal device, comprising the nanoparticle according to any one of claims 1-10, and a magnetic probe rod system with an flexible end, wherein the magnetic probe rod system comprises a handle, a flexible rod, a magnetic field source and a magnetically permeable material.
 18. The stone removal device according to claim 17, wherein the magnetic probe rod system is provided with an AC or DC power supply, a power switch, a DC battery compartment or an AC plug on the handle; the flexible rod is made of a polymer material, preferably the flexible rod includes a permanent magnet at its rear end and optionally a flexible magnetically permeable material at the end of the flexible rod.
 19. An article, the article comprising the nanoparticle according to any one of claims 1-10, wherein the nanoparticle is in form of a solution or a powder, preferably a solution.
 20. A use of the nanoparticle according to any one of claims 1 to 10 in the manufacture of an article for in-vivo stone removal, preferably the article is used for urinary stone removal in a human or animal. 